• 2022-06-29
    图所示电路中,电源线电压 [tex=4.071x1.214]bSYsjfYp40kNawIYmOuLKQ==[/tex]。 三个电阻性负载联结成星形,其电阻为[tex=9.857x1.214]htugxn5+XqZy88We/COg+nasnYQHOF1GMsrdhkZrdq5OL7TEXaADQNsBrdZO9Jzd[/tex](1) 试求负载相电压、相电流及中性线电流,并作相量图;(2)如无中性线,求负载相电压及中性点电压;(3)如无中性线,当 [tex=0.714x1.0]X6uqj1A7AQmRFBpFsTbZTg==[/tex] 相短路时,求各相电压和电流,并作相量图;(4)如无中性线,当 [tex=1.0x1.0]97Y4VMFIqE7cl6MEqnCpuw==[/tex] 相断路时,求另外两相的电压和电流; (5)在(3) 、 (4) 中如有中性线,则又如何?[img=228x216]1799195b1adbec3.png[/img]
  • 解(1) 此电路为不对称负载的三相四线制,因为有中性线,各相电压对称。[tex=10.214x2.714]Ey12Mh0jDCA9hXtGo+ZKl3j98huFBTzv4RhiVHGhfw0O4YhsTNrIqHHWMnUywWVZ3/ZyhcHnxdFSC5CAfBvLQvtnRr++XEEev4KvQ4ZhGmE=[/tex]各相电流为[tex=10.714x8.214]rZM5/OPAdr7aX+kNl9iwpBr+TISWt98l8ZuOkSzYIzQMTvc6HFk0m829QDdZfUk4MQJNwxTsnYF10yyInR1Wh1rugcPcP21rmfEgXn7CXTtS+mQcrrw/D2rLBimvZkyTe4qmuIYn9tdF0+CWdoBvdSbzynK+U0+D9Wad/ydcehiOTz8Y3Mcp2+VSdfgKMDzjLN8uufQ+ethZf4stoCUw/x2Rn/kCIyYTIucMS5B1LftsBi8W0D64QMym6Mgm4ru9+BBVlsId+iYUocDYmpnzyg==[/tex]设 [tex=5.643x1.429]Lrge11BaeoZfcOxCGEByMWU6YFQx/tu6ax/ZRSXHo0Xz8/QkSrIifJEDhqIF3sqQ[/tex] 为参考相量,则各相负载电压相量为设 [tex=5.643x1.429]Lrge11BaeoZfcOxCGEByMWU6YFQx/tu6ax/ZRSXHo0Xz8/QkSrIifJEDhqIF3sqQ[/tex] 为参考相量,则各相负载电压相量为[tex=20.5x1.429]DuAsDZuc88Ek7CBDS7ziExssYubv55R5IAQe5rjYca3YpsWJM8t3ktNsp9jssxcjz19oq2lokvYzT8uq1WI/ZiByOLw8worlq1jmCGYYgsWcuFK3MW8eXs8LDSi3Qk9GU1kZqgm0/r+9Q4/4grkCg3m90ghjlXrqbguihjXLa4g=[/tex]各相电流相量为[tex=18.857x1.429]S2wp6gNzYKTYaveZ8loZsF/ba7meWaJsMPKba9gTYmfTMtB6F30FfQHSjBXtfUkmLjfF9s/Vxpa198pdjLQEump56KX8yP69zDsIETRTevwHRBOyWKGElHc4ys6OJiEmsBlQrgMka2BmVoufQJEOtb9uw/yDzea3tYZ/m4/Q5yQ=[/tex]中性线电流为[tex=23.929x1.429]DubduJpEwMYgZqBOHhHmaJ0nA7Nz/envYlruwAC24Lt8kBBLVGeYxitG3kZPTBXHogMeq43nlgww/NNQ/lOyZ8OKjKJKrbs3aO3zrMY7BlT+HL8gxwS8R4ajOHZs5jTSoe0UD72MtAEjO6A4wg+XaRFheW0XPCZWisJiipLjIFA5bBfcAmj2w7e6PtEcGfJuZlN4nqnrouibjCWVN99Ccw==[/tex]相量图如图所示。[img=282x257]1799199405725b9.png[/img](2) 如无中性线,则电路如图所示,负载中性点与电源中性点间电压为[img=372x227]179919a02f904c6.png[/img][tex=25.714x3.429]MjaqUoup23rQd/5woQuAvU4ojy4oq0umXYrtFPwIeWi0Bi80qegaWSL1TURdGYSTm5x23I4R6ZdfZNtnTzyddD542zwe0zycAfcTeUrW7a/gLMh+Eloo4iU75SiK17TR0jeufnpldSPD0JRAL1Gsji2vL8m6jvrTgh5oBcpm0Jrh7v9ezTqAY2W94g/F3F7gsdUC72gMxmMBvt3rndJzHkoIOXZXIpYudSTzwU6jHL62CyP8TBwGADcuKm+4CWy9VwLJKOCpuMLVlfzl1xaxRlHHQfeenMvX/izhXNeyRv/NxP5Om4MTW9b3eefJgvDJ9C4TFZsq9EVibfvynfhy/u+fOSXeRUlO0fuy/WpvM8IGe0+pWF1+avJF7HEr5z7vUOoqXqA90ecIQJKGUL41M4nXfWo02GOlFtA24RBKCrF2isPCkrAhyCDMfq87Fhxjjv/bmjuyHDaJ2qcGT2JLLuF4WzoQurgRuUuDCmdKKDg=[/tex]此时各相负载电压为[tex=22.5x5.071]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[/tex](3) 如无中性线,且 [tex=0.714x1.0]X6uqj1A7AQmRFBpFsTbZTg==[/tex] 相短路时,各相负载电压为[tex=20.643x5.071]rZM5/OPAdr7aX+kNl9iwpNwMeh1tOnuFRR8Tvqs3Jb4m6wDeDjrPfH3w1ea0oeQwLNVWVaQ3IIDV7hctwKv7cMAi28eVqnNX6As7HEsOA5XQUW/JhFm8tMCZljhuc9W74X1Q21zRpnBTEd/uwIMJToLQYOK3qBu/9NOtvukcpyqjdWuFg2yWVHlgBnDZv8Fd448CjecCEryyMOXFVE2QQ9/8SmrqUOimqOt6dDcGjI6NxfLrvHi9wTzXGZ4Y4XlE77scltmkG51SYlRnWBwn5JT3nlED1QCNT+yXkhi8pmhCHb2Qe8vve8wmD6gRt6hMql8DM5X54Acqpy5aauYDnrBhqa/jcwcJNoGIRGisqY138bCiAsP835/XearP6CWK[/tex]各相负载电流为[tex=21.357x9.357]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[/tex]相量图如图所示。[img=350x295]179919e2ded6b69.png[/img](4) 如无中性线,且 [tex=1.0x1.0]0e+76hgEqXhGRszRQWFSzQ==[/tex] 相断路,则 [tex=2.786x1.214]TIG4GNJviD3ItHmp/qBSY1RKiMtddRFsqkq0uppA07E=[/tex] 串联 于线电压 [tex=1.429x1.429]sPJ2rHoGRz0n1JFFx5/p5oS6kFWOBovdR4brfA5Y6IQ=[/tex] 中,故[tex=19.929x6.357]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[/tex](5) 在(3) 中有中性线时,U 相短路,则 [tex=0.714x1.0]X6uqj1A7AQmRFBpFsTbZTg==[/tex] 相由于 电流过大而将熔断器熔断,[tex=0.643x1.0]SW0o8G0GHsmLXldwnq7xKg==[/tex]、[tex=1.0x1.0]0e+76hgEqXhGRszRQWFSzQ==[/tex] 相未受影响,其电压、电流与(1)中相同。对(4)中有中性线时,[tex=1.0x1.0]0e+76hgEqXhGRszRQWFSzQ==[/tex] 相断路,则 [tex=1.0x1.0]0e+76hgEqXhGRszRQWFSzQ==[/tex] 相电流为零,各相电压和电流与(1)相同。

    举一反三

    内容

    • 0

      已知三相电源的线电压[tex=3.786x1.214]i/QfSrA8GJVjtKU2ZfxQKF/c4BXjs1DmwxAkJPHbxZo=[/tex]。对称三相负载星形联结,每相负载的阻抗[tex=1.5x1.0]Hj3yOxrA+dFVodCWbjy5Wg==[/tex][tex=4.714x1.357]zcMwxUbrNzUZtGeXqR3sSqNuxZkyizRIJxRnu0FVJVM=[/tex]。试求: (1)负载的相电流及线电流; (2)画出相量图; (3)若输电线阻抗[tex=5.429x1.357]Efpfcy+Zrbt3nmySPz2nc/m2u7EXxm+ZfgTgaxbHcOE=[/tex],再求负载的相电流及线电流。

    • 1

      在如图9-27所示对称三相电路中,[tex=5.714x1.286]SGrFkMIZ0bqyerU3SNZtFt14HuzbVBgvFwIHtHlY8so4vXdaWWabUgDuPRrJiG+7yGcALd8k3MACTGIvG0fENQ==[/tex]负载阻抗[tex=7.0x1.357]p9Dz6tACDST+p8J/bNyo50BCrzjCKDzUjYAEjtmh9FW5Bv+JNmYzu6nTltjXYrkF[/tex]。试求(1)当U相负载发生短路时,负载各相的电压,并画出三相负载的线电压和相电压的相量图;(2)当U相负载断开时,负载各相的电压,并画出三相负载的线电压和相电压的相量图。[p=align:center][img=300x173]17e395638b41a95.png[/img]

    • 2

      4-2.已知对称三相电路每相负载的电阻R=8Q ,感抗XL=6Q。[br][/br](1)设电源电压U=380V。求负载星形连接时的相电压,相电流,线电流,并作相量图。[br][/br](2 )设电源电压U= 220V。求负载三角形连接时的相电压,相电流,线电流,并作相量图。[br][/br](3 )设电源电压U仍为380V。求负载三角形连接时的相电压,相电流,线电流又是多少?[br][/br](4)分析比较以上三种情况。当负载额定电压220V,电源线电压380V时和220V时两种情况下,各应如何连接?[br][/br]

    • 3

      在图题 6.7所示电路中已知[tex=14.714x1.571]3ltAidNs5xbpgCEuUyQZjfdZqWefQ+QbhCNoxjHXkzTGy3rbsNQH5c2KkfCpsZKD7p3SpyTGmVxYCZqzcoHfnJbdWQ+DTHGgkvj49EgIr51W7tFt9p8PnbNQj5+zJtGx7qDI/Vn3HGhYmN1zmV0JPQ==[/tex]求各元件的电压、电流及电源电压[tex=0.643x0.786]I4YEZdwKyeUepz5y5fKCxw==[/tex],并作各电压、电流相量图。 

    • 4

      6-2对 称三相电路的电源线电压为380V,三角形联结的对称负载[tex=6.214x1.357]+f73GUJtm9n46ie3tv+5x5Tiqvw+GcJI9tatoak+SN0=[/tex]。试求: (1)负载的相电流和线电流; (2) 画出相量图; (3) 若输电线阻抗[tex=5.429x1.357]CNz7myOA2VLv7yG2NqCDZtkh7rT5MA+kXbd9stzm7Ok=[/tex],再求负载的相电流和线电流。